A lawsuit may derail a project that was supposed to cost $45 billion and is now $70 billion and counting.

California's bullet train was conceived 20 years ago from Quentin Kopp's infatuation with European high-speed rail. His beautiful brainchild, however, has since morphed into a monstrosity. Mr. Kopp seems more and more like the protagonist Victor Frankenstein of literary lore, disillusioned by what his ambitions have wrought.

Testifying in a lawsuit filed by Kings County, the 84-year-old retired judge of San Mateo County Superior Court says that California's present high-speed rail plan violates the ballot measure that he...